Elementary Ca2+ signals through endothelial TRPV4 channels regulate vascular function

Regulation of Collecting Lymphatic Vessel Contractile Function by TRPV4 Channels

BACKGROUND

Dysregulation of TRPV4 (transient receptor potential vanilloid 4)-mediated signaling has been associated with inflammation and tissue fibrosis, both of which are key features in the pathophysiology of lymphatic system diseases; however, the expression and functional roles of lymphatic TRPV4 channels remain largely unexplored.

METHODS

We generated a single-cell RNA sequencing dataset from microdissected mouse collecting lymphatic vessels to characterize the expression of Trpv4. Using a novel Trpv4fx/fx mouse strain and the Cre-lines Prox1-CreERT2 and LysM-Cre we assessed the role of TRPV4 channels in lymphatic endothelial cells and peri-lymphatic myeloid cells, respectively. Confocal microscopy and extensive functional experimentation on isolated and pressurized lymphatics, including measurements of intracellular calcium activity, were used to validate our single-cell RNA sequencing findings and to elucidate the underlying mechanisms. Clinical significance was assessed using biopsies from patients with breast cancer-related lymphedema.

RESULTS

We characterized the single-cell transcriptome of collecting lymphatic vessels and surrounding tissues. Trpv4 was highly enriched in lymphatic endothelial cells and in a subset of Lyve1+ (lymphatic vessel endothelial hyaluronan receptor 1) macrophages displaying a tissue-resident profile. In clinical samples, breast cancer-related lymphedema was associated with increased infiltration of macrophages coexpressing LYVE1 and TRPV4. Pharmacological activation of TRPV4 channels led to contractile dysregulation in isolated collecting lymphatics. The response was multiphasic, including initial vasospasm and subsequent vasodilation and inhibition of contractions, which was associated with the activation of TXA2Rs (thromboxane A2 receptors) in lymphatic muscle cells by secreted prostanoids from TRPV4+ myeloid cells, and increased nitric oxide (and perhaps other vasodilatory prostanoids) from lymphatic endothelial cells. The TXA2R-mediated vasospasm resulted from increased mobilization of calcium from intracellular stores through inositol trisphosphate receptors and store-operated calcium entry.

CONCLUSIONS

Our results uncovered a novel mechanism of lymphatic contractile dysregulation mediated by the crosstalk between TRPV4-expressing myeloid cells, including LYVE1+ macrophages, and lymphatic muscle cells or lymphatic endothelial cells. These findings highlight potentially important roles of TRPV4 channels in lymphatic dysfunction associated with inflammation, including secondary lymphedema.

A Highly Adaptable Hydrogen Bond Re-Orientation (HyBRO) Strategy for Multiscale Vasculature Fabrication

Three-dimensional printing of microchannel networks mimicking native vasculature provides essential functions for biomedical applications. However, developing a highly "adaptable" technique - that can adjust to diverse materials choices, high shape accuracy, and broad size ranges - for producing physiologically responsive vasculature remains challenging. Here, an innovative hydrogen bond re-orientation (HyBRO) strategy for microchannel network fabrication is reported. By identifying interfacial instability of sacrificial material (SM) during embedding as a core limitation, this strategy prints the SM into an optimal "nonsolvent" to shape the desirable channel structure. In this process, the nonsolvent instantaneously switches the SM from forming hydrogen bonds with exterior water to forming interior linkages inside it. This transition protects the SM from external solvent "erosion" upon re-exposure to embedding material, inhibiting deformation. Consequently, this approach enables the creation of accurate (>90%), multiscale (10-fold), hierarchical microchannel networks, accommodating accurate printing of a wide range of ink materials - extending from typical hydrophilic polymers into non-typical hydrophobic ones. Further biological tests demonstrate that HyBRO-produced vasculature recapitulates not only essential endothelial barrier function but also delicate ion-channel responses to varying shear stresses, highlighting its potential for engineering physiologically responsive vasculature in broad applications.

Investigating the Role of TRPV4 and GPR35 Interaction in Endothelial Dysfunction in Aging Mice

Endothelial dysfunction, characterized by a decline in endothelial physiological functions, is a significant aspect of cardiovascular aging, contributing notably to arterial stiffness, atherosclerosis, and hypertension. Transient receptor potential channel V4 (TRPV4), a key member of Ca2+-permeable channels, plays a crucial role in maintaining vascular functions. However, the role and mechanisms of TRPV4 in aging-related endothelial dysfunction remain incompletely understood. Here, we demonstrated a marked reduction in endothelial TRPV4 function without alterations in its expression, leading to abnormal endothelial Ca2+ signaling and impaired vasodilation in aging mesenteric arteries. Employing transcriptome sequencing, co-IP, and PLA assays, we characterized G protein-coupled receptor 35 (GPR35) interacting with TRPV4, and abnormally enhanced interactions were found in aging endothelial cells. Subsequently, we revealed that intensive GPR35-TRPV4 interaction significantly contributes to endothelial dysfunction during aging, utilizing TRPV4 endothelial-specific knockout (TRPV4EC -/-), AAV-FLT1-shRNA (GPR35) mice, and GPR35 overexpressed/knocked-down HUVECs. Furthermore, molecular docking analysis and subsequent co-IP and pressure myograph experiments indicated that both Thonningianin A and Carfilzomib efficiently restored the GPR35-TRPV4 interaction, preventing endothelial dysfunction and vasodilation impairment. Our study identifies the crucial role of GPR35-TRPV4 interaction in aging-associated abnormal endothelial function and vascular tone modulation. Restoring GPR35-TRPV4 interaction via Thonningianin A or Carfilzomib represents a promising precision approach for aging-related endothelial dysfunction.

Pericyte Electrical Signalling and Brain Haemodynamics

Dynamic control of membrane potential lies at the nexus of a wide spectrum of biological processes, ranging from the control of individual cell secretions to the orchestration of complex thought and behaviour. Electrical signals in all vascular cell types (smooth muscle cells, endothelial cells and pericytes) contribute to the control of haemodynamics and energy delivery across spatiotemporal scales and throughout all tissues. Here, our goal is to review and synthesize key studies of electrical signalling within the brain vasculature and integrate these with recent data illustrating an important electrical signalling role for pericytes, in doing so attempting to work towards a holistic description of blood flow control in the brain by vascular electrical signalling. We use this as a framework for generating further questions that we believe are important to pursue. Drawing parallels with electrical signal integration in the nervous system may facilitate deeper insights into how signalling is organized within the vasculature and how it controls blood flow at the network level.

Optical Tweezer-Driven Mechanotransduction: Probing pN-Scale Forces and Calcium-Mediated Redox Signaling in Single Endothelial Cells

Endothelial cells (ECs) regulate vascular function by converting mechanical forces into biochemical signals; however, the molecular mechanisms of pN-scale mechanotransduction remain elusive. Here, we develop an optical tweezer-integrated confocal microscopy system that allows precise, noninvasive manipulation of the cell membrane localization with mechanical stimuli within the 0-100 pN range while monitoring Ca2+-mediated NO/ROS redox signaling in situ in single ECs under varying force parameters. We show that pN-scale mechanical stimulation regulates extracellular Ca2+ influx, triggering downstream production of NO and ROS, which subsequently affects intracellular redox homeostasis. Key mechanosensitive ion channels (e.g., Piezo1 and TRPV4) and cytoskeletal components (e.g., F-actin) facilitate force-induced redox signaling. We further delineate the roles of membrane tension-dominant versus hybrid tension-tether models in mechanotransduction, revealing their differential engagement in force transmission pathways. This mechanistic framework establishes direct connections between pN-scale mechanical input characteristics and redox-regulated vascular homeostasis.

Activation of APJ Receptors by CMF-019, But Not Apelin, Causes Endothelium-Dependent Relaxation of Spontaneously Hypertensive Rat Coronary Arteries

ABSTRACT

Receptors for the vasoactive adipokine apelin, termed APJ receptors, are G-protein-coupled receptors and are widely expressed throughout the cardiovascular system. APJ receptors can also signal through G-protein-independent pathways, including G-protein-coupled receptor kinase 2 (GRK2), which inhibits endothelial nitric oxide synthase (eNOS) activity and nitric oxide production in endothelial cells. Apelin causes endothelium-dependent, nitric oxide-mediated relaxation of coronary arteries from normotensive animals, but the effects of activating APJ receptor signaling pathways in hypertensive coronary arteries are largely unknown. We hypothesized that apelin-induced relaxation is impaired in coronary arteries from spontaneously hypertensive rats (SHR). Western blot and mRNA analysis revealed increased GRK2 expression in cultured SHR coronary endothelial cells. Apelin failed to cause relaxation in isolated SHR coronary arteries but, in the presence of apelin, relaxations to acetylcholine were impaired. Apelin had no effect on relaxation to diethylamine NONOate. The GRK2 inhibitor, CMPD101, increased apelin-induced phosphorylation of Akt and eNOS in SHR endothelial cells and restored relaxation to apelin in SHR arteries. CMPD101 also blocked the inhibitory effect of apelin on ACh-induced relaxation. Relaxations to the APJ receptor-biased agonist, CMF-019, which preferentially activates the G-protein-dependent pathway with minimal effect on GRK2, were similar in SHR and Wistar Kyoto coronary arteries. Immunoblot analysis in SHR coronary endothelial cells demonstrated that CMF-019 increased Akt and eNOS phosphorylation whereas apelin had no effect. Thus, APJ receptor signaling through GRK2 impairs nitric oxide production or release from SHR endothelial cells. APJ receptor-biased agonists, such as CMF-019, may be more effective than apelin in causing vasodilation of SHR coronary arteries.

TRPV4 Promotes Vascular Calcification by Directly Associating With and Activating β-Catenin

BACKGROUND

Vascular calcification contributes to increased cardiovascular morbidity and mortality in patients with chronic kidney disease, diabetes, and atherosclerosis. Currently, there are no effective therapeutic strategies to prevent or reverse vascular calcification. TRPV4 (transient receptor potential channel V4), a key Ca2+-permeable channel, plays an important role in various diseases. However, the role and mechanism of TRPV4 in vascular calcification have not yet been elucidated.

METHODS

The effects of TRPV4 on vascular calcification were explored in vitro and in vivo. TRPV4 interactome assessment and molecular docking were performed to investigate the mechanism and specific therapeutic strategy for vascular calcification.

RESULTS

TRPV4 was substantially upregulated in high inorganic phosphate-induced calcified vascular smooth muscle cells (SMCs) and calcified aortas from cholecalciferol (vitamin D3)-overloaded mice. TRPV4 overexpression increased the expression of the osteochondrogenic markers Runx2 (runt-related transcription factor 2), Msx2 (Msh homeobox 2), and Sox9 (SRY-box transcription factor 9) and exacerbated high inorganic phosphate-induced vascular SMC calcification in a Ca2+ influx-dependent manner. In contrast, TRPV4 deficiency or inactivation significantly inhibited vascular SMC calcification under high inorganic phosphate conditions. Moreover, compared with that in control littermates, SMC-specific TRPV4 deficiency in mice alleviated vitamin D3-induced and 5/6 nephrectomy-induced vascular calcification. Mechanistically, TRPV4 interacted with β-catenin and activated β-catenin/TCF (T-cell factor) transcriptional activity via Ca2+/ASK1 (apoptosis signal regulating kinase 1)/p38 signaling. β-Catenin knockdown abolished the effects of TRPV4 overexpression on vascular SMC calcification. TRPV4/β-catenin interaction is pivotal for maintaining TRPV4/Ca2+-induced ASK1/p38/β-catenin activation. Hesperidin, a natural product found in citrus fruits, effectively disrupted TRPV4/β-catenin interaction, thereby inhibiting ASK1/p38/β-catenin activity and preventing vascular calcification.

CONCLUSIONS

Our study identified TRPV4 as a new pathogenic factor for vascular calcification that directly associates with and activates β-catenin. Blocking the TRPV4/β-catenin interaction through hesperidin suppressed the progression of vascular calcification and may be an effective precision strategy to address vascular calcification.

Endothelial Cell Calcium Influx Mediates Trauma-induced Endothelial Permeability

OBJECTIVE

To investigate whether ex vivo plasma from injured patients causes endothelial calcium (Ca 2+ ) influx as a mechanism of trauma-induced endothelial permeability.

BACKGROUND

Endothelial permeability after trauma contributes to postinjury organ dysfunction. While the mechanisms remain unclear, emerging evidence suggests intracellular Ca 2+ signaling may play a role.

METHODS

Ex vivo plasma from injured patients with "low injury/low shock" (injury severity score <15, base excess ≥-6 mEq/L) and "high injury/high shock" (injury severity score ≥15, base excess <-6 mEq/L) were used to treat endothelial cells. Experimental conditions included Ca 2+ removal from the extracellular buffer, cyclopiazonic acid pretreatment to deplete intracellular Ca 2+ stores, and GSK2193874 pretreatment to block the transient receptor potential vanilloid 4 (TRPV4) Ca 2+ channel. Live cell fluorescence microscopy and electrical cell-substrate impedance sensing were used to assess cytosolic Ca 2+ increases and permeability, respectively. Western blot and live cell actin staining were used to assess myosin light chain phosphorylation and actomyosin contraction.

RESULTS

Compared with low injury/low shock plasma, high injury/high shock induced greater cytosolic Ca 2+ increase. Cytosolic Ca 2+ increase, myosin light chain phosphorylation, and actin cytoskeletal contraction were lower without extracellular Ca 2+ present. High injury/high shock plasma did not induce endothelial permeability without extracellular Ca 2+ present. TRPV4 inhibition lowered trauma plasma-induced endothelial Ca 2+ influx and permeability.

CONCLUSIONS

This study illuminates a novel mechanism of postinjury endotheliopathy involving Ca 2+ influx through the TRPV4 channel. TRPV4 inhibition mitigates trauma-induced endothelial permeability. Moreover, widespread endothelial Ca 2+ influx may contribute to trauma-induced hypocalcemia. This study provides the mechanistic basis for the development of Ca 2+ -targeted therapies and interventions in the care of severely injured patients.

Capsaicin inhibits porcine enteric coronaviruses replication through blocking TRPV4-mediated calcium ion influx

Porcine enteric coronaviruses, including transmissible gastroenteritis virus (TGEV), porcine epidemic diarrhea virus (PEDV) and porcine deltacoronavirus (PDCoV), have caused enormous economic losses to the global pig industry. Unfortunately, new variants emerge of these viruses will make it difficult for pigs vaccinated with the appropriate vaccine to develop protective immunity. Hence, it is urgent to explore effective therapeutic agents and targets against these viruses. Capsaicin is an active compound found in plants of the Capsicum genus (prevention and/or treatment of pain, hypertension and inflammation), but little is known about its effects on enterovirus infections. Herein, we used porcine enteric coronavirus TGEV as a model to evaluate the antiviral activity of capsaicin and discovered that capsaicin inhibited the replication phase of TGEV. Mechanistically, calcium signaling pathway participates in the capsaicin-mediated antiviral function. Importantly, capsaicin treatment impaired the viral replication by attenuating cytosolic calcium, and supplementation with CaCl2 reduced the inhibitory effect of capsaicin on TGEV infection. Finally, we revealed that TRPV4 plays an essential role in modulating calcium ion influx in IPEC-J2 cells, and capsaicin inhibits TGEV replication by decreasing calcium ion influx through inhibition of TRPV4. Overall, our data suggest that capsaicin is a promising small molecular drug candidate for strengthening host resistance to porcine enteric coronavirus infection.

Flow-sensitive ion channels in vascular endothelial cells: Mechanisms of activation and roles in mechanotransduction

The purpose of this review is to evaluate the current knowledge about the mechanisms by which mechanosensitive ion channels are activated by fluid shear stress in endothelial cells. We focus on three classes of endothelial ion channels that are most well studied for their sensitivity to flow and roles in mechanotransduction: inwardly rectifying K+ channels, Piezo channels, and TRPV channels. We also discuss the mechanisms by which these channels initiate and contribute to mechanosensitive signaling pathways. Three types of mechanisms have been described for flow-induced activation of ion channels: 1) through interaction with apical membrane flow sensors, such as glycocalyx, which is likely to be deformed by flow, 2) directly by sensing membrane stretch that is induced by shear stress, or 3) via flow-sensitive channel-channel or lipid channel interactions. We also demonstrate the physiological role of these channels and how they are related to cardiovascular and neurological diseases. Further studies are needed to determine how these channels function cooperatively to mediate the endothelial response to flow.

Imaging Ca2+ Signals in Small Pulmonary Veins at Physiological Intraluminal Pressures

Pulmonary veins (PVs) carry oxygen-rich blood from the lungs back to the left heart, thus serving an important function in the delivery of oxygen-rich blood to vital organs. However, most studies of pulmonary vasculature have focused on pulmonary arteries and capillaries under normal and disease conditions. Ca2+ signals are critical regulators of vascular function. Despite the critical physiological roles of PVs, Ca2+ signals in small intrapulmonary PVs have not been recorded under physiological conditions. Here, we describe a technique to record Ca2+ signal activity in mouse PVs isolated, cannulated and pressurized at 5 mmHg. By incorporating a Ca2+ indicator, we can study Ca2+ signals in the myocyte layer of small PVs using high-speed, spinning disk confocal imaging under physiological conditions. Our representative data indicates that the Ca2+ signals in small PV myocytes are mediated by openings of ryanodine receptor ion channels. This method will be of considerable interest to researchers in the field of pulmonary vascular physiology and disorders.

TRPV4 in Cerebral Small Vessel Disease: A key interacting partner

Cerebral small vessel disease (cSVD) is a major cause of vascular cognitive impairment and dementia. The underlying disease mechanisms are centered around the dysfunction of the neurovascular unit and include an impairment of the blood-brain barrier (BBB) permeability, a decreased cerebrovascular reactivity and cerebral hypoperfusion. The cells composing the neurovascular unit express a wide variety of mechanosensitive ion channels that are relevant for these processes. Recent research has increasingly focused on the mechanobiology of cerebral microvessels with recent evidence pointing towards a significant role of transient receptor potential vanilloid 4 (TRPV4). This Ca2+-permeable channel regulates key physiological functions, including vascular tone, angiogenesis, BBB integrity and neuroinflammation. Beyond its physiological role, recent evidence implicates TRPV4 in pathological processes such as cerebrovascular remodelling, impaired cerebrovascular reactivity, and BBB dysfunction. In this review, we explore the multiple roles of TRPV4 within the neurovascular unit, its interactions with key molecular partners, and we discuss evidence for its potential contribution to cSVD.

The antioxidant property of CAPE depends on TRPV1 channel activation in microvascular endothelial cells

Caffeic acid phenethyl ester (CAPE) is a hydrophobic phytochemical typically found in propolis that acts as an antioxidant, anti-inflammatory and cardiovascular protector, among several other properties. However, the molecular entity responsible for recognising CAPE is unknown, and whether that molecular interaction is involved in developing an antioxidant response in the target cells remains an unanswered question. Herein, we hypothesized that a subfamily of TRP ion channels works as the molecular entity that recognizes CAPE at the plasma membrane and allows a fast shift in the antioxidant capacity of intact endothelial cells (EC). By monitoring cytoplasmic Ca2+ in a microvascular EC model, we compared the calcium responses evoked by three structurally related compounds: caffeic acid phenethyl ester, neochlorogenic acid and caffeic acid. Only CAPE induced rapid and transient calcium responses at nanomolar concentrations together with a gradual increase in cytoplasmic sodium levels, suggesting the activation of a non-selective cationic permeation at the plasma membrane. Electrophysiological as well as pharmacological, and RNA silencing assays confirmed the involvement of TRPV1 in the recognition of CAPE by ECs. Finally, we demonstrated that Ca2+ influx by TRPV1 was necessary for recording CAPE-induced cytoplasmic redox changes, a phenomenon captured in real-time in ECs expressing the HyPer biosensor. Our data depict a molecular mechanism behind the antioxidant effect of CAPE in endothelial cells, connecting the activation of TRPV1 ion channels, cytoplasmic calcium increase, and a reduction of disulfide bonds on a redox biosensor. This phenomenon occurs within seconds to minutes and contributes to a better understanding of the mechanisms underlying the vasodilatory effect of CAPE and other compounds that interact with TRPV1 in the vascular bed.

Endothelial TRPV4-Cx43 signalling complex regulates vasomotor tone in resistance arteries

S-nitrosylation of Cx43 gap junction channels critically regulates communication between smooth muscle cells and endothelial cells. This post-translational modification also induces the opening of undocked Cx43 hemichannels. However, its specific impact on vasomotor regulation remains unclear. Considering the role of endothelial TRPV4 channel activation in promoting vasodilatation through nitric oxide (NO) production, we investigated the direct modulation of endothelial Cx43 hemichannels by TRPV4 channel activation. Using the proximity ligation assay, we identified that Cx43 and TRPV4 are found in close proximity in the endothelium of resistance arteries. In primary endothelial cell (EC) cultures from resistance arteries, GSK 1016790A-induced TRPV4 activation enhances eNOS activity, increases NO production, and opens Cx43 hemichannels via direct S-nitrosylation. Notably, the elevated intracellular Ca2+ levels caused by TRPV4 activation were reduced by blocking Cx43 hemichannels. In ex vivo mesenteric arteries, inhibiting Cx43 hemichannels reduced endothelial hyperpolarization without affecting NO production in ECs, underscoring a critical role of TRPV4-Cx43 signalling in endothelial electrical behaviour. We perturbed the proximity of Cx43/TRPV4 by disrupting lipid rafts in ECs using β-cyclodextrin. Under these conditions, hemichannel activity, Ca2+ influx and endothelial hyperpolarization were blunted upon GSK stimulation. Intravital microscopy of mesenteric arterioles in vivo further demonstrated that inhibiting Cx43 hemichannel activity, NO production and disrupting endothelial integrity reduce TRPV4-induced relaxation. These findings underscore a new pivotal role of the Cx43 hemichannel associated with the TRPV4 signalling pathway in modulating endothelial electrical behaviour and vasomotor tone regulation. KEY POINTS: TRPV4-Cx43 interaction in endothelial cells: the study reveals a close proximity between Cx43 proteins and TRPV4 channels in endothelial cells of resistance arteries, establishing a functional interaction that is critical for vascular regulation. S-nitrosylation of Cx43 hemichannels: TRPV4 activation via GSK treatment induces S-nitrosylation of Cx43, facilitating the opening of Cx43 hemichannels. TRPV4-mediated calcium signalling: activation of TRPV4 leads to increased intracellular Ca2+ levels in endothelial cells, an effect that is mitigated by the inhibition of Cx43 hemichannels, indicating a regulatory feedback mechanism between these two channels. Endothelial hyperpolarization and vasomotor regulation: Blocking Cx43 hemichannels impairs endothelial hyperpolarization in mesenteric arteries, without affecting NO production, suggesting a role for Cx43 in modulating endothelial electrical behaviour and contributing to vasodilatation. In vivo role of Cx43 hemichannels in vasodilatation: intravital microscopy of mouse mesenteric arterioles demonstrated that inhibiting Cx43 hemichannel activity and disrupting endothelial integrity significantly impair TRPV4-induced vasodilatation, highlighting the crucial role of Cx43 in regulating endothelial function and vascular relaxation.

Targeting gut S. aureofaciens Tü117 serves as a new potential therapeutic intervention for the prevention and treatment of hypertension

Currently, the regulation of specific gut microbial metabolism for the development and/or treatment of hypertension remains largely unexplored. Here, we show that α-lipomycin, produced by Streptomyces aureofaciens (S. aureofaciens) Tü117, is upregulated in the serum of high-salt diet (HSD) mice and patients with essential hypertension. α-lipomycin causes vasodilation impairment involving transient receptor potential vanilloid 4 (TRPV4)-mediated nitric oxide and endothelium-derived hyperpolarizing factor pathways in mice. We also find that Lactobacillus plantarum (L. plantarum) CCFM639 attenuates the increase in blood pressure (BP) potentially through inhibiting the proliferation of S. aureofaciens Tü117 in mice. An exploratory intervention trial indicates that L. plantarum CCFM639 supplementation reduces BPs in subjects newly diagnosed with pre-hypertension or stage 1 hypertension without antihypertensive medication. Our findings provide evidence for a role of S. aureofaciens Tü117-associated α-lipomycin elevation in the pathogenesis of HSD-induced hypertension, highlighting that targeting gut bacteria serves as a new therapeutic intervention for hypertension.

The Roles of Transient Receptor Potential (TRP) Channels Underlying Aberrant Calcium Signaling in Blood-Retinal Barrier Dysfunction

The inner blood-retinal barrier (iBRB) protects the retinal vasculature from the peripheral circulation. Endothelial cells (ECs) are the core component of the iBRB; their close apposition and linkage via tight junctions limit the passage of fluids, proteins, and cells from the bloodstream to the parenchyma. Dysfunction of the iBRB is a hallmark of many retinal disorders. Vascular endothelial growth factor (VEGF) has been identified as the primary driver leading to a dysfunctional iBRB, thereby becoming the main target for therapy. However, a complete understanding of the molecular mechanisms underlying iBRB dysfunction is elusive and alternative therapeutic targets remain unexplored. Calcium (Ca2+) is a universal intracellular messenger whose homeostasis and dynamics are dysregulated in many pathological disorders. Among the extensive components of the cellular Ca2+-signaling toolkit, cation-selective transient receptor potential (TRP) channels are broadly involved in cell physiology and disease and, therefore, are widely studied as possible targets for therapy. Albeit that TRP channels have been discovered in the photoreceptors of Drosophila and have been studied in the neuroretina, their presence and function in the iBRB have only recently emerged. Within this article, we discuss the structure and functions of the iBRB with a particular focus on Ca2+ signaling in retinal ECs and highlight the potential of TRP channels as new targets for retinal diseases.

Flow-Dependent Modulation of Endothelial Ca2+ Dynamics by Small Conductance Ca2+-Activated K+ Channels in Mouse Carotid Arteries

BACKGROUND

Small conductance Ca2+ activated K+ channels (KCa2.3) are important regulators of vascular function. They provide Ca2+-dependent hyperpolarization of the endothelial membrane potential, promoting agonist-induced vasodilation. Another important mechanism of influence may occur through positive feedback regulation of endothelial Ca2+ signals, likely via amplification of influx through membrane cation channels. KCa2.3 channels have recently been implicated in flow-mediated dilation of the arterial vasculature and may contribute to the crucial homeostatic role of shear stress in preventing vascular wall remodeling and progressive vascular disease (i.e., atherosclerosis). The impact of KCa2.3 channels on endothelial Ca2+ signaling under physiologically relevant shear stress conditions remains unknown.

METHODS

In the current study, we employ mice expressing an endothelium-specific Ca2+ fluorophore (cdh5-GCaMP8) to characterize the KCa2.3 channel influence on the dynamic Ca2+ signaling profile along the arterial endothelium in the presence and absence of shear-stress.

RESULTS

Our data indicate KCa2.3 channels have a minimal influence on basal Ca2+ signaling in the carotid artery endothelium in the absence of flow, but they contribute substantially to amplification of Ca2+ dynamics in the presence of flow and their influence can be augmented through exogenous positive modulation.

CONCLUSIONS

The findings suggest a pivotal role for KCa2.3 channels in adjusting the profile of homeostatic dynamic Ca2+ signals along the arterial intima under flow.

Peptide Lv and Angiogenesis: A Newly Discovered Angiogenic Peptide

Peptide Lv is a small endogenous secretory peptide with ~40 amino acids and is highly conserved among certain several species. While it was first discovered that it augments L-type voltage-gated calcium channels (LTCCs) in neurons, thus it was named peptide "Lv", it can bind to vascular endothelial growth factor receptor 2 (VEGFR2) and has VEGF-like activities, including eliciting vasodilation and promoting angiogenesis. Not only does peptide Lv augment LTCCs in neurons and cardiomyocytes, but it also promotes the expression of intermediate-conductance KCa channels (KCa3.1) in vascular endothelial cells. Peptide Lv is upregulated in the retinas of patients with early proliferative diabetic retinopathy, a disease involving pathological angiogenesis. This review will provide an overview of peptide Lv, its known bioactivities in vitro and in vivo, and its clinical relevance, with a focus on its role in angiogenesis. As there is more about peptide Lv to be explored, this article serves as a foundation for possible future developments of peptide Lv-related therapeutics to treat or prevent diseases.

TMAO Impairs Mouse Aortic Vasodilation by Inhibiting TRPV4 Channels in Endothelial Cells

Trimethylamine oxide (TMAO) is an intestinal flora metabolite associated with risk of cardiovascular diseases. Transient receptor potential vanilloid 4 (TRPV4) is a Ca2+-permeable ion channel that is essential for vasodilation and endothelial function. Currently, there are few studies on the effect of TMAO on TRPV4 channels. In the present study, Ca2+ imaging of vascular tissue showed that TMAO inhibited TRPV4-mediated Ca2+ influx into aortic endothelial cells in a dose-dependent manner. Furthermore, a whole-cell patch clamp assay showed that TMAO blocked TRPV4-mediated cation currents. Notably, results of aortic vascular tension measurement showed that TMAO impaired endothelium-dependent vasodilation in mouse aortic vessels through the TRPV4-NO pathway. Our results indicated that TMAO inhibited Ca2+ entry in endothelial cells and impaired vasodilation through the TRPV4-NO pathway in mice. These results provide scientific evidence for novel pathogenic mechanisms underlying the role of TMAO in cardiovascular disease.

DISTINCT PATTERNS OF ENDOTHELIAL CELL ACTIVATION PRODUCED BY EXTRACELLULAR HISTONES AND BACTERIAL LIPOPOLYSACCHARIDE

ABSTRACT

Objective : Vascular endothelial cells (ECs) sense and respond to both trauma factors (histone proteins) and sepsis signals (bacterial lipopolysaccharide, LPS) with elevations in calcium (Ca 2+ ), but it is not clear if the patterns of activation are similar or different. We hypothesized that within seconds of exposure, histones but not LPS would produce a large EC Ca 2+ response. We also hypothesized that histones would produce different spatio-temporal patterns of Ca 2+ events in veins than in arteries. Methods : We studied cultured ECs (EA.hy926) and native endothelial cells from surgically opened murine blood vessels. High-speed live cell imaging of Ca 2+ events were acquired for 5 min before and after stimulation of cultured ECs with histones or LPS alone or in combination. Histone-induced EC Ca 2+ events were also compared in native endothelial cells from resistance-sized arteries and veins. Ca 2+ activity was quantified as "Ca 2+ prevalence" using custom spatiotemporal analysis. Additionally, cultured ECs were collected after 6 h of exposure to histones or LPS for RNA sequencing. Results : ECs-both in culture and in blood vessels-rapidly increased Ca 2+ activity within seconds of histone exposure. In contrast, LPS exposure produced only a slight increase in Ca 2+ activity in cultured ECs and no effect on blood vessels over 5-min recording periods. Histones evoked large aberrant Ca 2+ events (>30 s in duration) in both veins and arteries, but with different spatio-temporal patterns. Ca 2+ activity in arterial ECs often appeared as "rosettes", with Ca 2+ events that propagated from one cell to all adjacent surrounding cells. In veins, ECs responded individually without spreading. Surprisingly, exposure of cultured ECs to LPS for 5 min before histones potentiated EC Ca 2+ activity by an order of magnitude. Exposure of ECs to histones or LPS both increased gene expression, but different mRNAs were induced. Conclusions : LPS and histones activate ECs through mechanisms that are distinct and additive; only histones produce large aberrant Ca 2+ events. ECs in arteries and veins display different patterns of Ca 2+ responses to histones.

Thirty years of Ca2+ spark research: digital principle of cell signaling unveiled

Calcium ions (Ca2+) are an archetypical and most versatile second messenger in virtually all cell types. Inspired by the discovery of Ca2+ sparks in the 1990s, vibrant research over the last three decades has unveiled a constellation of Ca2+ microdomains as elementary events of Ca2+ signaling and, more importantly, a digital-analog dualism as the system design principle of Ca2+ signaling. In this brief review, we present a sketchy summary on advances in the field of sparkology, and discuss how the digital subsystem can fulfill physiological roles otherwise impossible for any analog system. In addition, we attempt to address how the digital-analog dualism endows the simple cation messenger with signaling speediness, specificity, efficiency, stability, and unparalleled versatility.

Mechanosensory entities and functionality of endothelial cells

The endothelial cells of the blood circulation are exposed to hemodynamic forces, such as cyclic strain, hydrostatic forces, and shear stress caused by the blood fluid's frictional force. Endothelial cells perceive mechanical forces via mechanosensors and thus elicit physiological reactions such as alterations in vessel width. The mechanosensors considered comprise ion channels, structures linked to the plasma membrane, cytoskeletal spectrin scaffold, mechanoreceptors, and junctional proteins. This review focuses on endothelial mechanosensors and how they alter the vascular functions of endothelial cells. The current state of knowledge on the dysregulation of endothelial mechanosensitivity in disease is briefly presented. The interplay in mechanical perception between endothelial cells and vascular smooth muscle cells is briefly outlined. Finally, future research avenues are highlighted, which are necessary to overcome existing limitations.

Ion Channels Remodeling in the Regulation of Vascular Hyporesponsiveness During Shock

Shock is characterized with vascular hyporesponsiveness to vasoconstrictors, thereby to cause refractory hypotension, insufficient tissue perfusion, and multiple organ dysfunction. The vascular hyporeactivity persisted even though norepinephrine and fluid resuscitation were administrated, it is of critical importance to find new potential target. Ion channels are crucial in the regulation of cell membrane potential and affect vasoconstriction and vasodilation. It has been demonstrated that many types of ion channels including K+ channels, Ca2+ permeable channels, and Na+ channels exist in vascular smooth muscle cells and endothelial cells, contributing to the regulation of vascular homeostasis and vasomotor function. An increasing number of studies suggested that the structural and functional alterations of ion channels located in arteries contribute to vascular hyporesponsiveness during shock, but the underlying mechanisms remained to be fully clarified. Therefore, the expression and functional changes in ion channels in arteries associated with shock are reviewed, to pave the way for further exploring the potential of ion channel-targeted compounds in treating refractory hypotension in shock.

Mitochondrial Ca2+-coupled generation of reactive oxygen species, peroxynitrite formation, and endothelial dysfunction in Cantú syndrome

Cantú syndrome is a multisystem disorder caused by gain-of-function (GOF) mutations in KCNJ8 and ABCC9, the genes encoding the pore-forming inward rectifier Kir6.1 and regulatory sulfonylurea receptor SUR2B subunits, respectively, of vascular ATP-sensitive K+ (KATP) channels. In this study, we investigated changes in the vascular endothelium in mice in which Cantú syndrome-associated Kcnj8 or Abcc9 mutations were knocked in to the endogenous loci. We found that endothelium-dependent dilation was impaired in small mesenteric arteries from Cantú mice. Loss of endothelium-dependent vasodilation led to increased vasoconstriction in response to intraluminal pressure or treatment with the adrenergic receptor agonist phenylephrine. We also found that either KATP GOF or acute activation of KATP channels with pinacidil increased the amplitude and frequency of wave-like Ca2+ events generated in the endothelium in response to the vasodilator agonist carbachol. Increased cytosolic Ca2+ signaling activity in arterial endothelial cells from Cantú mice was associated with elevated mitochondrial [Ca2+] and enhanced reactive oxygen species (ROS) and peroxynitrite levels. Scavenging intracellular or mitochondrial ROS restored endothelium-dependent vasodilation in the arteries of mice with KATP GOF mutations. We conclude that mitochondrial Ca2+ overload and ROS generation, which subsequently leads to nitric oxide consumption and peroxynitrite formation, cause endothelial dysfunction in mice with Cantú syndrome.

Endothelial TRPV4/Cx43 Signaling Complex Regulates Vasomotor Tone in Resistance Arteries

S-nitrosylation of Cx43 gap junction channels critically regulates communication between smooth muscle cells and endothelial cells. This posttranslational modification also induces the opening of undocked Cx43 hemichannels. However, its specific impact on vasomotor regulation remains unclear. Considering the role of endothelial TRPV4 channel activation in promoting vasodilation through nitric oxide (NO) production, we investigated the direct modulation of endothelial Cx43 hemichannels by TRPV4 channel activation. Using the proximity ligation assay, we identify that Cx43 and TRPV4 are found in close proximity in the endothelium of resistance arteries. In primary endothelial cell cultures from resistance arteries (ECs), GSK-induced TRPV4 activation enhances eNOS activity, increases NO production, and opens Cx43 hemichannels via direct S-nitrosylation. Notably, the elevated intracellular Ca2+ levels caused by TRPV4 activation were reduced by blocking Cx43 hemichannels. In ex vivo mesenteric arteries, inhibiting Cx43 hemichannels reduced endothelial hyperpolarization without affecting NO production in ECs, underscoring a critical role of TRPV4/Cx43 signaling in endothelial electrical behavior. We perturbed the proximity of Cx43/TRPV4 by disrupting lipid rafts in ECs using β-cyclodextrin. Under these conditions, hemichannel activity, Ca2+ influx, and endothelial hyperpolarization were blunted upon GSK stimulation. Intravital microscopy of mesenteric arterioles in vivo further demonstrated that inhibiting Cx43 hemichannels activity, NO production and disrupting endothelial integrity reduce TRPV4-induced relaxation. These findings underscore a new pivotal role of Cx43 hemichannel associated with TRPV4 signaling pathway in modulating endothelial electrical behavior and vasomotor tone regulation.

Role of transient receptor potential channels in the regulation of vascular tone

Vascular tone is a major element in the control of hemodynamics. Transient receptor potential (TRP) channels conducting monovalent and/or divalent cations (e.g. Na+ and Ca2+) are expressed in the vasculature. Accumulating evidence suggests that TRP channels participate in regulating vascular tone by regulating intracellular Ca2+ signaling in both vascular smooth muscle cells (VSMCs) and endothelial cells (ECs). Aberrant expression/function of TRP channels in the vasculature is associated with vascular dysfunction in systemic/pulmonary hypertension and metabolic syndromes. This review intends to summarize our current knowledge of TRP-mediated regulation of vascular tone in both physiological and pathophysiological conditions and to discuss potential therapeutic approaches to tackle abnormal vascular tone due to TRP dysfunction.

Interaction between TRP channels and anoctamins

Anoctamin 1 (ANO1) binds to transient receptor potential (TRP) channels (protein-protein interaction) and then is activated by TRP channels (functional interaction). TRP channels are non-selective cation channels that are expressed throughout the body and play roles in multiple physiological functions. Studies on TRP channels increased after the identification of TRP vanilloid 1 (TRPV1) in 1997. Calcium-activated chloride channel anoctamin 1 (ANO1, also called TMEM16A and DOG1) was identified in 2008. ANO1 plays a major role in TRP channel-mediated functions, as first shown in 2014 with the demonstration of a protein-protein interaction between TRPV4 and ANO1. In cells that co-express TRP channels and ANO1, calcium entering cells through activated TRP channels causes ANO1 activation. Therefore, in many tissues, the physiological functions related to TRP channels are modulated through chloride flux associated with ANO1 activation. In this review, we summarize the latest understanding of TRP-ANO1 interactions, particularly interaction of ANO1 with TRPV4, TRP canonical 6 (TRPC6), TRPV3, TRPV1, and TRPC2 in the salivary glands, blood vessels, skin keratinocytes, primary sensory neurons, and vomeronasal organs, respectively.

CaMKII activity and metabolic imbalance-related neurological diseases: Focus on vascular dysfunction, synaptic plasticity, amyloid beta accumulation, and lipid metabolism

Metabolic syndrome (MetS) is characterized by insulin resistance, hyperglycemia, excessive fat accumulation and dyslipidemia, and is known to be accompanied by neuropathological symptoms such as memory loss, anxiety, and depression. As the number of MetS patients is rapidly increasing globally, studies on the mechanisms of metabolic imbalance-related neuropathology are emerging as an important issue. Ca2+/calmodulin-dependent kinase II (CaMKII) is the main Ca2+ sensor and contributes to diverse intracellular signaling in peripheral organs and the central nervous system (CNS). CaMKII exerts diverse functions in cells, related to mechanisms such as RNA splicing, reactive oxygen species (ROS) generation, cytoskeleton, and protein-protein interactions. In the CNS, CaMKII regulates vascular function, neuronal circuits, neurotransmission, synaptic plasticity, amyloid beta toxicity, lipid metabolism, and mitochondrial function. Here, we review recent evidence for the role of CaMKII in neuropathologic issues associated with metabolic disorders.

TRPV4-Expressing Tissue-Resident Macrophages Regulate the Function of Collecting Lymphatic Vessels via Thromboxane A2 Receptors in Lymphatic Muscle Cells

Rationale

TRPV4 channels are critical regulators of blood vascular function and have been shown to be dysregulated in many disease conditions in association with inflammation and tissue fibrosis. These are key features in the pathophysiology of lymphatic system diseases, including lymphedema and lipedema; however, the role of TRPV4 channels in the lymphatic system remains largely unexplored. TRPV4 channels are calcium permeable, non-selective cation channels that are activated by diverse stimuli, including shear stress, stretch, temperature, and cell metabolites, which may regulate lymphatic contractile function.

Objective

To characterize the expression of TRPV4 channels in collecting lymphatic vessels and to determine the extent to which these channels regulate the contractile function of lymphatics.

Methods and Results

Pressure myography on intact, isolated, and cannulated lymphatic vessels showed that pharmacological activation of TRPV4 channels with GSK1016790A (GSK101) led to contractile dysregulation. The response to GSK101 was multiphasic and included, 1) initial robust constriction that was sustained for ≥1 minute and in some instances remained for ≥4 minutes; and 2) subsequent vasodilation and partial or complete inhibition of lymphatic contractions associated with release of nitric oxide. The functional response to activation of TRPV4 channels displayed differences across lymphatics from four anatomical regions, but these differences were consistent across different species (mouse, rat, and non-human primate). Importantly, similar responses were observed following activation of TRPV4 channels in arterioles. The initial and sustained constriction was prevented with the COX inhibitor, indomethacin. We generated a controlled and spatially defined single-cell RNA sequencing (scRNAseq) dataset from intact and microdissected collecting lymphatic vessels. Our data uncovered a subset of macrophages displaying the highest expression of Trpv4 compared to other cell types within and surrounding the lymphatic vessel wall. These macrophages displayed a transcriptomic profile consistent with that of tissue-resident macrophages (TRMs), including differential expression of Lyve1 , Cd163 , Folr2 , Mrc1 , Ccl8 , Apoe , Cd209f , Cd209d , and Cd209g ; and at least half of these macrophages also expressed Timd4. This subset of macrophages also highly expressed Txa2s , which encodes the thromboxane A2 (TXA2) synthase. Inhibition of TXA2 receptors (TXA2Rs) prevented TRPV4-mediated contractile dysregulation. TXA2R activation on LMCs caused an increase in mobilization of calcium from intracellular stores through Ip3 receptors which promoted store operated calcium entry and vasoconstriction.

Conclusions

Clinical studies have linked cancer-related lymphedema with an increased infiltration of macrophages. While these macrophages have known anti-inflammatory and pro-lymphangiogenic roles, as well as promote tissue repair, our results point to detrimental effects to the pumping capacity of collecting lymphatic vessels mediated by activation of TRPV4 channels in macrophages. Pharmacological targeting of TRPV4 channels in LYVE1-expressing macrophages or pharmacological targeting of TXA2Rs may offer novel therapeutic strategies to improve lymphatic pumping function and lymph transport in lymphedema.

Mechanosensitive membrane domains regulate calcium entry in arterial endothelial cells to protect against inflammation

Endothelial cells (ECs) in the descending aorta are exposed to high laminar shear stress, and this supports an antiinflammatory phenotype. High laminar shear stress also induces flow-aligned cell elongation and front-rear polarity, but whether these are required for the antiinflammatory phenotype is unclear. Here, we showed that caveolin-1-rich microdomains polarize to the downstream end of ECs that are exposed to continuous high laminar flow. These microdomains were characterized by high membrane rigidity, filamentous actin (F-actin), and raft-associated lipids. Transient receptor potential vanilloid (TRPV4) ion channels were ubiquitously expressed on the plasma membrane but mediated localized Ca2+ entry only at these microdomains where they physically interacted with clustered caveolin-1. These focal Ca2+ bursts activated endothelial nitric oxide synthase within the confines of these domains. Importantly, we found that signaling at these domains required both cell body elongation and sustained flow. Finally, TRPV4 signaling at these domains was necessary and sufficient to suppress inflammatory gene expression and exogenous activation of TRPV4 channels ameliorated the inflammatory response to stimuli both in vitro and in vivo. Our work revealed a polarized mechanosensitive signaling hub in arterial ECs that dampened inflammatory gene expression and promoted cell resilience.

Non-neuronal cell-derived acetylcholine, a key modulator of the vascular endothelial function in health and disease

Vascular endothelial cells play an important role in regulating peripheral circulation by modulating arterial tone in the microvasculature. Elevated intracellular Ca2+ levels are required in endothelial cells to induce smooth muscle relaxation via endothelium-dependent mechanisms such as nitric oxide production, prostacyclin, and endothelial cell hyperpolarization. It is well established that exogenous administration of acetylcholine can increase intracellular Ca2+ concentrations, followed by endothelium-dependent vasodilation. Although endogenous acetylcholine's regulation of vascular tone remains debatable, recent studies have reported that endogenously derived acetylcholine, but not neuronal cell-derived acetylcholine, is a key modulator of endothelial cell function. In this minireview, we summarize the current knowledge of the non-neuronal cholinergic system (NNCS) in vascular function, particularly vascular endothelial cell function, which contributes to blood pressure regulation. We also discuss the possible pathophysiological impact of endothelial NNCS, which may induce the development of vascular diseases due to endothelial dysfunction, and the potential of endothelial NNCS as a novel therapeutic target for endothelial dysfunction in the early stages of metabolic syndrome, diabetes, and hypertension.

WNK kinase is a vasoactive chloride sensor in endothelial cells

Endothelial cells (ECs) line the wall of blood vessels and regulate arterial contractility to tune regional organ blood flow and systemic pressure. Chloride (Cl-) is the most abundant anion in ECs and the Cl- sensitive With-No-Lysine (WNK) kinase is expressed in this cell type. Whether intracellular Cl- signaling and WNK kinase regulate EC function to alter arterial contractility is unclear. Here, we tested the hypothesis that intracellular Cl- signaling in ECs regulates arterial contractility and examined the signaling mechanisms involved, including the participation of WNK kinase. Our data obtained using two-photon microscopy and cell-specific inducible knockout mice indicated that acetylcholine, a prototypical vasodilator, stimulated a rapid reduction in intracellular Cl- concentration ([Cl-]i) due to the activation of TMEM16A, a Cl- channel, in ECs of resistance-size arteries. TMEM16A channel-mediated Cl- signaling activated WNK kinase, which phosphorylated its substrate proteins SPAK and OSR1 in ECs. OSR1 potentiated transient receptor potential vanilloid 4 (TRPV4) currents in a kinase-dependent manner and required a conserved binding motif located in the channel C terminus. Intracellular Ca2+ signaling was measured in four dimensions in ECs using a high-speed lightsheet microscope. WNK kinase-dependent activation of TRPV4 channels increased local intracellular Ca2+ signaling in ECs and produced vasodilation. In summary, we show that TMEM16A channel activation reduces [Cl-]i, which activates WNK kinase in ECs. WNK kinase phosphorylates OSR1 which then stimulates TRPV4 channels to produce vasodilation. Thus, TMEM16A channels regulate intracellular Cl- signaling and WNK kinase activity in ECs to control arterial contractility.

Intrinsic and Extrinsic Contributors to the Cardiac Benefits of Exercise

Among its many cardiovascular benefits, exercise training improves heart function and protects the heart against age-related decline, pathological stress, and injury. Here, we focus on cardiac benefits with an emphasis on more recent updates to our understanding. While the cardiomyocyte continues to play a central role as both a target and effector of exercise's benefits, there is a growing recognition of the important roles of other, noncardiomyocyte lineages and pathways, including some that lie outside the heart itself. We review what is known about mediators of exercise's benefits-both those intrinsic to the heart (at the level of cardiomyocytes, fibroblasts, or vascular cells) and those that are systemic (including metabolism, inflammation, the microbiome, and aging)-highlighting what is known about the molecular mechanisms responsible.

Transient Receptor Potential Channels in the Healthy and Diseased Blood-Brain Barrier

The large family of transient receptor potential (TRP) channels are integral membrane proteins that function as environmental sensors and act as ion channels after activation by mechanical (touch), physical (heat, pain), and chemical stimuli (pungent compounds such as capsaicin). Most TRP channels are localized in the plasma membrane of cells but some of them are localized in membranes of organelles and function as intracellular Ca2+-ion channels. TRP channels are involved in neurological disorders but their precise role(s) and relevance in these disorders are not clear. Endothelial cells of the blood-brain barrier (BBB) express TRP channels such as TRP vanilloid 1-4 and are involved in thermal detection by regulating BBB permeability. In neurological disorders, TRP channels in the BBB are responsible for edema formation in the brain. Therefore, drug design to modulate locally activity of TRP channels in the BBB is a hot topic. Today, the application of TRP channel antagonists against neurological disorders is still limited.

KCNQ5 Controls Perivascular Adipose Tissue-Mediated Vasodilation

BACKGROUND

Small arteries exhibit resting tone, a partially contracted state that maintains arterial blood pressure. In arterial smooth muscle cells, potassium channels control contraction and relaxation. Perivascular adipose tissue (PVAT) has been shown to exert anticontractile effects on the blood vessels. However, the mechanisms by which PVAT signals small arteries, and their relevance remain largely unknown. We aimed to uncover key molecular components in adipose-vascular coupling.

METHODS

A wide spectrum of genetic mouse models targeting Kcnq3, Kcnq4, and Kcnq5 genes (Kcnq3-/-, Kcnq4-/-, Kcnq5-/-, Kcnq5dn/dn, Kcnq4-/-/Kcnq5dn/dn, and Kcnq4-/-/Kcnq5-/-), telemetry blood pressure measurements, targeted lipidomics, RNA-Seq profiling, wire-myography, patch-clamp, and sharp-electrode membrane potential measurements was used.

RESULTS

We show that PVAT causes smooth muscle cell KV7.5 family of voltage-gated potassium (K+) channels to hyperpolarize the membrane potential. This effect relaxes small arteries and regulates blood pressure. Oxygenation of polyunsaturated fats generates oxylipins, a superclass of lipid mediators. We identified numerous oxylipins released by PVAT, which potentiate vasodilatory action in small arteries by opening smooth muscle cell KV7.5 family of voltage-gated potassium (K+) channels.

CONCLUSIONS

Our results reveal a key molecular function of the KV7.5 family of voltage-gated potassium (K+) channels in the adipose-vascular coupling, translating PVAT signals, particularly oxylipins, to the central physiological function of vasoregulation. This novel pathway opens new therapeutic perspectives.

Mechanosensing by Vascular Endothelium

Mechanical forces influence different cell types in our bodies. Among the earliest forces experienced in mammals is blood movement in the vascular system. Blood flow starts at the embryonic stage and ceases when the heart stops. Blood flow exposes endothelial cells (ECs) that line all blood vessels to hemodynamic forces. ECs detect these mechanical forces (mechanosensing) through mechanosensors, thus triggering physiological responses such as changes in vascular diameter. In this review, we focus on endothelial mechanosensing and on how different ion channels, receptors, and membrane structures detect forces and mediate intricate mechanotransduction responses. We further highlight that these responses often reflect collaborative efforts involving several mechanosensors and mechanotransducers. We close with a consideration of current knowledge regarding the dysregulation of endothelial mechanosensing during disease. Because hemodynamic disruptions are hallmarks of cardiovascular disease, studying endothelial mechanosensing holds great promise for advancing our understanding of vascular physiology and pathophysiology.

Electro-metabolic signaling

Precise matching of energy substrate delivery to local metabolic needs is essential for the health and function of all tissues. Here, we outline a mechanistic framework for understanding this critical process, which we refer to as electro-metabolic signaling (EMS). All tissues exhibit changes in metabolism over varying spatiotemporal scales and have widely varying energetic needs and reserves. We propose that across tissues, common signatures of elevated metabolism or increases in energy substrate usage that exceed key local thresholds rapidly engage mechanisms that generate hyperpolarizing electrical signals in capillaries that then relax contractile elements throughout the vasculature to quickly adjust blood flow to meet changing needs. The attendant increase in energy substrate delivery serves to meet local metabolic requirements and thus avoids a mismatch in supply and demand and prevents metabolic stress. We discuss in detail key examples of EMS that our laboratories have discovered in the brain and the heart, and we outline potential further EMS mechanisms operating in tissues such as skeletal muscle, pancreas, and kidney. We suggest that the energy imbalance evoked by EMS uncoupling may be central to cellular dysfunction from which the hallmarks of aging and metabolic diseases emerge and may lead to generalized organ failure states-such as diverse flavors of heart failure and dementia. Understanding and manipulating EMS may be key to preventing or reversing these dysfunctions.

Flow-dependent regulation of rat mesenteric lymphatic vessel contractile response requires activation of endothelial TRPV4 channels

OBJECTIVES

The objective of our study is to evaluate the involvement of the transient receptor potential vanilloid 4 (TRPV4) in the alteration of lymphatic pumping in response to flow and determine the signaling pathways involved.

METHODS

We used immunofluorescence imaging and western blotting to assess TRPV4 expression in rat mesenteric lymphatic vessels. We examined inhibition of TRPV4 with HC067047, nitric oxide synthase (NOS) with L-NNA and cyclooxygenases (COXs) with indomethacin on the contractile response of pressurized lymphatic vessels to flow changes induced by a stepwise increase in pressure gradients, and the functionality of endothelial TRPV4 channels by measuring the intracellular Ca2+ response of primary lymphatic endothelial cell cultures to the selective agonist GSK1016790A.

RESULTS

TRPV4 protein was expressed in both the endothelial and the smooth muscle layer of rat mesenteric lymphatics with high endothelial expression around the valve sites. When maintained under constant transmural pressure, most lymphatic vessels displayed a decrease in contraction frequency under conditions of flow and this effect was ablated through inhibition of NOS, COX or TRPV4.

CONCLUSIONS

Our findings demonstrate a critical role for TRPV4 in the decrease in contraction frequency induced in lymphatic vessels by increases in flow rate via the production and action of nitric oxide and dilatory prostanoids.

TRPV4 is expressed by enteric glia and muscularis macrophages of the colon but does not play a prominent role in colonic motility

Background

Mechanosensation is an important trigger of physiological processes in the gastrointestinal tract. Aberrant responses to mechanical input are associated with digestive disorders, including visceral hypersensitivity. Transient Receptor Potential Vanilloid 4 (TRPV4) is a mechanosensory ion channel with proposed roles in visceral afferent signaling, intestinal inflammation, and gut motility. While TRPV4 is a potential therapeutic target for digestive disease, current mechanistic understanding of how TRPV4 may influence gut function is limited by inconsistent reports of TRPV4 expression and distribution.

Methods

In this study we profiled functional expression of TRPV4 using Ca2+ imaging of wholemount preparations of the mouse, monkey, and human intestine in combination with immunofluorescent labeling for established cellular markers. The involvement of TRPV4 in colonic motility was assessed in vitro using videomapping and contraction assays.

Results

The TRPV4 agonist GSK1016790A evoked Ca2+ signaling in muscularis macrophages, enteric glia, and endothelial cells. TRPV4 specificity was confirmed using TRPV4 KO mouse tissue or antagonist pre-treatment. Calcium responses were not detected in other cell types required for neuromuscular signaling including enteric neurons, interstitial cells of Cajal, PDGFRα+ cells, and intestinal smooth muscle. TRPV4 activation led to rapid Ca2+ responses by a subpopulation of glial cells, followed by sustained Ca2+ signaling throughout the enteric glial network. Propagation of these waves was suppressed by inhibition of gap junctions or Ca2+ release from intracellular stores. Coordinated glial signaling in response to GSK1016790A was also disrupted in acute TNBS colitis. The involvement of TRPV4 in the initiation and propagation of colonic motility patterns was examined in vitro.

Conclusions

We reveal a previously unappreciated role for TRPV4 in the initiation of distension-evoked colonic motility. These observations provide new insights into the functional role of TRPV4 activation in the gut, with important implications for how TRPV4 may influence critical processes including inflammatory signaling and motility.

Role of TRP Channels in Metabolism-Related Diseases

Metabolic syndrome (MetS), with its high prevalence and significant impact on cardiovascular disease, poses a substantial threat to human health. The early identification of pathological abnormalities related to MetS and prevention of the risk of associated diseases is of paramount importance. Transient Receptor Potential (TRP) channels, a type of nonselective cation channel, are expressed in a variety of tissues and have been implicated in the onset and progression of numerous metabolism-related diseases. This study aims to review and discuss the expression and function of TRP channels in metabolism-related tissues and blood vessels, and to elucidate the interactions and mechanisms between TRP channels and metabolism-related diseases. A comprehensive literature search was conducted using keywords such as TRP channels, metabolic syndrome, pancreas, liver, oxidative stress, diabetes, hypertension, and atherosclerosis across various academic databases including PubMed, Google Scholar, Elsevier, Web of Science, and CNKI. Our review of the current research suggests that TRP channels may be involved in the development of metabolism-related diseases by regulating insulin secretion and release, lipid metabolism, vascular functional activity, oxidative stress, and inflammatory response. TRP channels, as nonselective cation channels, play pivotal roles in sensing various intra- and extracellular stimuli and regulating ion homeostasis by osmosis. They present potential new targets for the diagnosis or treatment of metabolism-related diseases.

The conducted vasomotor response and the principles of electrical communication in resistance arteries

Biological tissues are fed by arterial networks whose task is to set blood flow delivery in accordance with energetic demand. Coordinating vasomotor activity among hundreds of neighboring segments is an essential process, one dependent upon electrical information spreading among smooth muscle and endothelial cells. The "conducted vasomotor response" is a functional expression of electrical spread, and it is this process that lies at the heart of this critical review. Written in a narrative format, this review first highlights historical manuscripts and then characterizes the conducted response across a range of preparations. Trends are highlighted and used to guide subsequent sections, focused on cellular foundations, biophysical underpinnings, and regulation in health and disease. Key information has been tabulated; figures reinforce grounding concepts and reveal a framework within which theoretical and experimental work can be rationalized. This summative review highlights that despite 30 years of concerted experimentation, key aspects of the conducted response remain ill defined. Of note is the need to rationalize the regulation and deterioration of conduction in pathobiological settings. New quantitative tools, along with transgenic technology, are discussed as a means of propelling this investigative field forward.

Evidence for the involvement of TRPV2 channels in the modulation of vascular tone in the mouse aorta

AIMS

Transient receptor potential vanilloid 2 (TRPV2) channels are expressed in both smooth muscle and endothelial cells and participate in vascular mechanotransduction and sensing of high temperatures and lipids. Nevertheless, the impact of TRPV2 channel activation by agonists on the coordinated and cell-type specific modulation of vasoreactivity is unknown.

MAIN METHODS

Aorta from 2- to 4-months-old male Oncins France 1 mice was dissected and mounted in tissue baths for isometric tension measurements. TRPV2 channel expression was assessed by immunofluorescence and western blot in mice aortas and in cultured A7r5 rat aortic smooth muscle cells.

KEY FINDINGS

TRPV2 channels were expressed in all three mouse aorta layers. Activation of TRPV2 channels with probenecid evoked endothelium-dependent relaxations through a mechanism that involved activation of smooth muscle Kir and Kv channels. In addition, TRPV2 channel inhibition with tranilast increased endothelium-independent relaxations to probenecid and this effect was abrogated by the KATP channel blocker glibenclamide, revealing that smooth muscle TRPV2 channels induce negative feedback on probenecid relaxations mediated via KATP channel inhibition. Exposure to the NO donor sodium nitroprusside increased TRPV2 channel translocation to the plasma membrane in cultured smooth muscle cells and enhanced negative feedback on probenecid relaxations.

SIGNIFICANCE

In conclusion, we present the first evidence that TRPV2 channels may modulate vascular tone through a balance of opposed inputs from the endothelium and the smooth muscle leading to net vasodilation. The fact that TRPV2 channel-induced activity can be amplified by NO emphasizes the pathophysiological relevance of these findings.

Myoendothelial feedback in mouse mesenteric resistance arteries is similar between the sexes, dependent on nitric oxide synthase, and independent of TPRV4

Myoendothelial feedback (MEF), the endothelium-dependent vasodilation following sympathetic vasoconstriction (mediated by smooth muscle to endothelium gap junction communication), has been well studied in resistance arteries of males, but not females. We hypothesized that MEF responses would be similar between the sexes, but different in the relative contribution of the underlying nitric oxide and hyperpolarization mechanisms, given that these mechanisms differ between the sexes in agonist-induced endothelium-dependent dilation. We measured MEF responses (diameter changes) of male and female first- to second-order mouse mesenteric arteries to phenylephrine (10 µM) over 30 min using isolated pressure myography ± blinded inhibition of nitric oxide synthase (NOS) using Nω-nitro-l-arginine methyl ester (l-NAME; 0.1-1.0 mM), hyperpolarization using 35 mM KCl, or transient receptor potential vanilloid 4 (TRPV4) channels using GSK219 (0.1-1.0 µM) or RN-1734 (30 µM). MEF was similar [%dilation (means ± SE): males = 26.7 ± 2.0 and females = 26.1 ± 1.9 at 15 min] and significantly inhibited by l-NAME (1.0 mM) at 15 min [%dilation (means ± SE): males = 8.2 ± 3.3, P < 0.01; females = 6.8 ± 1.9, P < 0.001] and over time (P < 0.01) in both sexes. l-NAME (0.1 mM) + 35 mM KCl nearly eliminated MEF in both sexes (P < 0.001-0.0001). Activation of TRPV4 with GSK101 (0.1-10 µM) induced similar dilation between the sexes. Inhibition of TRPV4, which is reportedly involved in the hyperpolarization mechanism, did not inhibit MEF in either sex. Similar expression of eNOS was found between the sexes with Western blot. Thus, MEF is prominent and similar in murine first- and second-order mesenteric resistance arteries of both sexes, and reliant primarily on NOS and secondarily on hyperpolarization, but not TRPV4.NEW & NOTEWORTHY We found that female mesenteric resistance arteries have similar postconstriction dilatory responses (i.e., myoendothelial feedback) to a sympathetic neurotransmitter analog as male arteries. Both sexes use nitric oxide synthase (NOS) and hyperpolarization, but not TRPV4, in this response. Moreover, the key protein involved in this pathway (eNOS) is similarly expressed in these arteries between the sexes. These similarities are surprising given that agonist-induced endothelium-dependent dilatory mechanisms differ in these arteries between the sexes.

Hyperoside ameliorates cerebral ischaemic-reperfusion injury by opening the TRPV4 channel in vivo through the IP3-PKC signalling pathway

CONTEXT

Hyperoside (Hyp), one of the active flavones from Rhododendron (Ericaceae), has beneficial effects against cerebrovascular disease. However, the effect of Hyp on vasodilatation has not been elucidated.

OBJECTIVE

To explore the effect of Hyp on vasodilatation in the cerebral basilar artery (CBA) of Sprague-Dawley (SD) rats suffering with ischaemic-reperfusion (IR) injury.

MATERIALS AND METHODS

Sprague-Dawley rats were randomly divided into sham, model, Hyp, Hyp + channel blocker and channel blocker groups. Hyp (50 mg/kg, IC₅₀ = 18.3 μg/mL) and channel blocker were administered via tail vein injection 30 min before ischaemic, followed by 20 min of ischaemic and 2 h of reperfusion. The vasodilation, hyperpolarization, ELISA assay, haematoxylin-eosin (HE), Nissl staining and channel-associated proteins and qPCR were analysed. Rat CBA smooth muscle cells were isolated to detect the Ca²⁺ concentration and endothelial cells were isolated to detect apoptosis rate.

RESULTS

Hyp treatment significantly ameliorated the brain damage induced by IR and evoked endothelium-dependent vasodilation rate (47.93 ± 3.09% vs. 2.99 ± 1.53%) and hyperpolarization (-8.15 ± 1.87 mV vs. -0.55 ± 0.42 mV) by increasing the expression of IP3R, PKC, transient receptor potential vanilloid channel 4 (TRPV4), IK_Ca and SK_Ca in the CBA. Moreover, Hyp administration significantly reduced the concentration of Ca²⁺ (49.08 ± 7.74% vs. 83.52 ± 6.93%) and apoptosis rate (11.27 ± 1.89% vs. 23.44 ± 2.19%) in CBA. Furthermore, these beneficial effects of Hyp were blocked by channel blocker.

DISCUSSION AND CONCLUSIONS

Although Hyp showed protective effect in ischaemic stroke, more clinical trial certification is needed due to the difference between animals and humans.

Angiotensin II induces endothelial dysfunction and vascular remodeling by downregulating TRPV4 channels

Angiotensin II (Ang II) is a potent vasoconstrictor of vascular smooth muscle cells (VSMC) and is implicated in hypertension, but it's role in the regulation of endothelial function is not well known. We and others have previously shown that mechanically activated ion channel, Transient Receptor Potential Vanilloid 4 (TRPV4) mediates flow- and/or receptor-dependent vasodilation via nitric oxide (NO) production in endothelial cells. Ang II was demonstrated to crosstalk with TRPV4 via angiotensin 1 receptor (AT1R) and β-arrestin signaling in epithelial and immortalized cells, however, the role of this crosstalk in endothelial cell function is not fully explored. Ang II treatment significantly downregulated TRPV4 protein expression and TRPV4-mediated Ca2+ influx in human EC without altering TRPV4 mRNA levels. Further, TRPV4-induced eNOS phosphorylation and NO production were significantly reduced in Ang II-treated human EC. Importantly, Ang II infusion in mice revealed that, TRPV4/p-eNOS expression and colocalization was reduced in endothelium in vivo. Finally, Ang II infusion induced vascular remodeling as evidenced by decreased lumen to wall ratio in resistant mesenteric arteries. These findings suggest that Ang II induces endothelial dysfunction and vascular remodeling via downregulation of TRPV4/eNOS pathway and may contribute to hypertension, independent of or in addition to its effect on vascular smooth muscle contraction.

Cracking the Endothelial Calcium (Ca2+) Code: A Matter of Timing and Spacing

A monolayer of endothelial cells lines the innermost surface of all blood vessels, thereby coming into close contact with every region of the body and perceiving signals deriving from both the bloodstream and parenchymal tissues. An increase in intracellular Ca2+ concentration ([Ca2+]i) is the main mechanism whereby vascular endothelial cells integrate the information conveyed by local and circulating cues. Herein, we describe the dynamics and spatial distribution of endothelial Ca2+ signals to understand how an array of spatially restricted (at both the subcellular and cellular levels) Ca2+ signals is exploited by the vascular intima to fulfill this complex task. We then illustrate how local endothelial Ca2+ signals affect the most appropriate vascular function and are integrated to transmit this information to more distant sites to maintain cardiovascular homeostasis. Vasorelaxation and sprouting angiogenesis were selected as an example of functions that are finely tuned by the variable spatio-temporal profile endothelial Ca2+ signals. We further highlighted how distinct Ca2+ signatures regulate the different phases of vasculogenesis, i.e., proliferation and migration, in circulating endothelial precursors.

Role of TRPV4 on vascular tone regulation in pathophysiological states

Vascular tone regulation is a key event in controlling blood flow in the body. Endothelial cells (ECs) and vascular smooth muscle cells (VSMCs) help regulate the vascular tone. Abnormal vascular responsiveness to various stimuli, including constrictors and dilators, has been observed in pathophysiological states although EC and VSMC coordinate to maintain the exquisite balance between contraction and relaxation in vasculatures. Thus, investigating the mechanisms underlying vascular tone abnormality is very important in maintaining vascular health and treating vasculopathy. Increased intracellular free Ca2+ concentration ([Ca2+]i) is one of the major triggers initiating each EC and VSMC response. Transient receptor potential vanilloid family member 4 (TRPV4) is a Ca2+-permeable non-selective ion channel, which is activated by several stimuli, and is presented in both ECs and VSMCs. Therefore, TRPV4 plays an important role in vascular responses. Emerging evidence indicates the role of TRPV4 on the functions of ECs and VSMCs in various pathophysiological states, including hypertension, diabetes, and obesity. This review focused on the link between TRPV4 and the functions of ECs/VSMCs, particularly its role in vascular tone and responsiveness to vasoactive substances.

The TMEM16A anion channel as a versatile regulator of vascular tone

The TMEM16A channel represents a key depolarizing mechanism in arterial smooth muscle and contractile pericytes, where it is activated by several endogenous contractile agonists. In this issue of Science Signaling, Mata-Daboin et al. demonstrate a previously unidentified role for TMEM16A in endothelial cells for acetylcholine-mediated vasorelaxation. Collectively, TMEM16A serves as a transducer of vasoactive stimuli to enable fine modulation of vessel tone.

Vasodilators activate the anion channel TMEM16A in endothelial cells to reduce blood pressure

Systemic blood pressure is acutely controlled by total peripheral resistance as determined by the diameter of small arteries and arterioles, the contractility of which is regulated by endothelial cells lining the lumen of blood vessels. We investigated the physiological functions of the chloride (Cl-) channel TMEM16A in endothelial cells. TMEM16A channels generated calcium (Ca2+)-activated Cl- currents in endothelial cells from control (TMEM16Afl/fl) mice that were absent in those from mice with tamoxifen-inducible, endothelial cell-specific knockout of TMEM16A (TMEM16A ecKO). TMEM16A currents in endothelial cells were activated by the muscarinic receptor agonist acetylcholine and an agonist of the Ca2+ channel TRPV4, which localized in nanoscale proximity with TMEM16A as assessed by single-molecule localization imaging of endothelial cells. Acetylcholine stimulated TMEM16A currents by activating Ca2+ influx through surface TRPV4 channels without altering the nanoscale properties of TMEM16A and TRPV4 surface clusters or their colocalization. In pressurized arteries, activation of TMEM16A channels in endothelial cells induced by acetylcholine; TRPV4 channel stimulation; or intraluminal ATP, another vasodilator, produced hyperpolarization and dilation. Furthermore, deficiency of TMEM16A channels in endothelial cells resulted in increased systemic blood pressure in conscious mice. These data indicate that vasodilators stimulate TRPV4 channels, leading to Ca2+-dependent activation of nearby TMEM16A channels in endothelial cells to produce arterial hyperpolarization, vasodilation, and reduced blood pressure. Thus, TMEM16A is an anion channel in endothelial cells that regulates arterial contractility and blood pressure.